CN112824664A

CN112824664A - Control device for internal combustion engine

Info

Publication number: CN112824664A
Application number: CN202011286076.7A
Authority: CN
Inventors: 井户侧正直; 今井创一
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2019-11-21
Filing date: 2020-11-17
Publication date: 2021-05-21
Also published as: JP2021080896A

Abstract

A control device for an internal combustion engine performs idle rotation speed control for controlling the idle rotation speed of the internal combustion engine to a target idle rotation speed. The idle rotation speed control is a feedback control for adjusting the output torque of the internal combustion engine by a feedback value calculated based on a deviation between a target idle rotation speed and an actual idle rotation speed. The control device is configured to execute a protection process for limiting the feedback value by the upper limit guard value and the lower limit guard value, and a modification process for modifying at least one of the upper limit guard value and the lower limit guard value so that the feedback range is wider when the engine temperature is low than when the engine temperature is high, when the range between the upper limit guard value and the lower limit guard value is set as the feedback range.

Description

Control device for internal combustion engine

Technical Field

The present invention relates to a control device for an internal combustion engine.

Background

For example, as disclosed in japanese patent application laid-open No. 2012 and 97703, in an internal combustion engine mounted on a vehicle or the like, idle rotation speed control is performed in which an idle rotation speed is feedback-controlled so as to be equal to a target idle rotation speed. The idle rotation speed control is a feedback control in which the actual idle rotation speed is made to approach the target idle rotation speed by adjusting the output torque of the internal combustion engine by a feedback value calculated from the deviation between the actual idle rotation speed and the target idle rotation speed.

Disclosure of Invention

Problems to be solved by the invention

However, when the temperature of the internal combustion engine is low, such as when the engine is cold, the viscosity of the lubricating oil in the internal combustion engine increases, and the viscosity at such a low temperature varies depending on the type of the lubricating oil. Such a difference in viscosity according to the type of the lubricating oil is greater at low temperatures of the internal combustion engine than at high temperatures. Here, the lubricating oil having a high viscosity at low temperature is referred to as a high-viscosity lubricating oil, and the lubricating oil having a relatively low viscosity at low temperature is referred to as a low-viscosity lubricating oil. In this case, when the feedback control is applied, the feedback control is preferably applied assuming that a high-viscosity lubricating oil having a large friction is used in the internal combustion engine at a low temperature so that the amount of adjustment of the output torque according to the deviation is not insufficient.

On the other hand, if the feedback control is applied assuming that a high-viscosity lubricating oil is used, the following problems may occur. That is, when a low-viscosity lubricant having a smaller friction than a high-viscosity lubricant is used at low temperatures, the amount of adjustment of the output torque according to the deviation becomes excessively large with respect to the friction. Therefore, the engine speed greatly varies, and for example, the quick rise of the engine speed may occur (japanese translation り from wind け). Since the deviation becomes large when such a large variation in the engine speed occurs, the output torque is adjusted by feedback control so as to converge such a large variation in the engine speed. However, when the variation in the engine speed is excessively large, the feedback value corresponding to the deviation is limited to an upper limit guard value that defines an upper limit of the feedback value and a lower limit guard value that defines a lower limit of the feedback value. Therefore, the actual feedback value is smaller than the feedback value corresponding to the deviation. Therefore, the fluctuation of the engine speed may hardly converge, and the controllability of the engine speed by the idle speed control may deteriorate.

Means for solving the problems

The control device for an internal combustion engine, which solves the above-described problem, performs idle rotation speed control for controlling the idle rotation speed of the internal combustion engine to a target idle rotation speed. The idle rotation speed control is a feedback control for adjusting the output torque of the internal combustion engine by a feedback value calculated based on a deviation between a target idle rotation speed and an actual idle rotation speed. The control device is configured to execute a protection process of limiting the feedback value by an upper limit guard value and a lower limit guard value, and a modification process of modifying at least one of the upper limit guard value and the lower limit guard value so that the feedback range is wider when the engine temperature is low than when the engine temperature is high, when the range between the upper limit guard value and the lower limit guard value is set as the feedback range.

According to this configuration, the feedback range is changed so as to be wider when the engine temperature is low than when the engine temperature is high. Therefore, the feedback range is widened at a low temperature of the internal combustion engine where a viscosity difference is likely to occur depending on the lubricant.

If the feedback range is widened in this manner, the adjustment range of the output torque based on the feedback value is widened. Therefore, even if the engine speed fluctuates greatly at a low temperature of the engine due to the use of the low-viscosity lubricating oil, the fluctuation is converged by the adjustment of the output torque. Therefore, the controllability of the engine speed by the idle speed control is improved.

In the control device, the changing process may be a process of changing the upper limit guard value so that the upper limit guard value becomes larger when the engine temperature is low than when the engine temperature is high.

According to this configuration, when the engine temperature is low, the upper limit guard value becomes a larger value than when the engine temperature is high. Therefore, when the engine temperature is low, the adjustment range in the direction in which the output torque increases based on the feedback value becomes wider than when the engine temperature is high. Therefore, even when the actual idle rotation speed is significantly reduced from the target idle rotation speed at the time of low temperature of the internal combustion engine, the output torque can be sufficiently increased, and therefore the actual idle rotation speed can be increased to converge on the target idle rotation speed.

In the control device, the changing process may be a process of changing the lower limit guard value so that the lower limit guard value becomes smaller when the engine temperature is low than when the engine temperature is high.

According to this configuration, when the engine temperature is low, the lower limit guard value becomes smaller than when the engine temperature is high. Therefore, when the engine temperature is low, the adjustment range in the direction in which the output torque decreases based on the feedback value is increased as compared to when the engine temperature is high. Therefore, even when the actual idle rotation speed greatly exceeds the target idle rotation speed at the time of low temperature of the internal combustion engine, the output torque can be sufficiently reduced, so that the actual idle rotation speed can be reduced to converge to the target idle rotation speed.

Drawings

Fig. 1 is a schematic diagram showing a configuration of an internal combustion engine according to an embodiment to which a control device is applied.

Fig. 2 is a flowchart showing processing steps executed by the control device of the embodiment.

Fig. 3 is a schematic diagram showing the relationship between various values calculated by the control device of the embodiment.

Fig. 4 is a graph showing the relationship between the cooling water temperature and the 2 nd upper limit protection value and the 2 nd lower limit protection value calculated by the control device of the embodiment.

Fig. 5 is a graph showing the relationship between the cooling water temperature and the 2 nd upper limit guard value and the 2 nd lower limit guard value in the modification of the embodiment.

Fig. 6 is a graph showing the relationship between the cooling water temperature and the 2 nd upper limit guard value and the 2 nd lower limit guard value in the modification of the embodiment.

Fig. 7 is a graph showing the relationship between the cooling water temperature and the 2 nd upper limit guard value and the 2 nd lower limit guard value in the modification of the embodiment.

Fig. 8 is a graph showing the relationship between the cooling water temperature and the 2 nd upper limit guard value and the 2 nd lower limit guard value in the modification of the embodiment.

Fig. 9 is a graph showing the relationship between the cooling water temperature and the 2 nd upper limit guard value and the 2 nd lower limit guard value in the modification of the embodiment.

Description of the reference numerals

1 … internal combustion engine;

100 … control device;

110 … Central Processing Unit (CPU);

120 … memory.

Detailed Description

Hereinafter, an embodiment embodying the control apparatus of the internal combustion engine will be described with reference to fig. 1 to 4.

As shown in fig. 1, an internal combustion engine 1 includes a cylinder block 2 and a cylinder head 3, and lubricating oil is supplied to the inside of the internal combustion engine 1 to reduce sliding resistance. A cylinder 21 is provided in the cylinder block 2. The piston 22 is housed in the cylinder 21 so as to be capable of reciprocating. The reciprocating motion of the piston 22 is transmitted to a crankshaft 25 via a connecting rod 24, and the output of the internal combustion engine 1 is taken out from the crankshaft 25. Various auxiliary machines 26 driven by the output of the internal combustion engine 1 are drivably connected to the crankshaft 25. Examples of the auxiliary machine 26 include a compressor of an air conditioner, a power steering pump, a hydraulic pump, and an alternator.

A combustion chamber 23 surrounded by the inner peripheral surface of the cylinder 21, the top surface of the piston 22, and the cylinder head 3 is formed in the cylinder 21.

The cylinder head 3 is provided with an intake port 31 and an exhaust port 32. An intake pipe 33 is connected to the intake port 31, and an exhaust pipe 34 is connected to the exhaust port 32. The intake port 31 and the combustion chamber 23 are communicated and blocked by opening and closing operations of the intake valve 35, and the exhaust port 32 and the combustion chamber 23 are communicated and blocked by opening and closing operations of the exhaust valve 36. Further, a fuel injection valve 39 that injects fuel into the intake port 31 is provided in the intake port 31.

An ignition plug 37 for igniting an air-fuel mixture, which is a mixture of fuel and air, by a spark, is disposed in a portion of the cylinder head 3 that forms the top of the combustion chamber 23.

A surge tank 40 is provided in the intake pipe 33, and a throttle valve 38 for adjusting the flow rate of air flowing through the intake pipe 33 is provided upstream of the surge tank 40.

Various controls of the internal combustion engine 1 are performed by the control device 100. The control device 100 includes a central processing unit (hereinafter, referred to as a CPU)110, and electronic components such as a memory 120 in which programs and data for control are stored. The control device 100 executes various control-related processes by the CPU110 executing programs stored in the memory 120.

Various sensors such as an air flow meter 91 that detects an intake air amount GA of the internal combustion engine 1, a water temperature sensor 92 that detects a cooling water temperature THW that is a temperature of cooling water of the internal combustion engine 1, a crank angle sensor 93 that detects a crank angle of the crankshaft 25, an air throttle sensor 94 that detects a throttle opening TA that is an opening degree of the throttle valve 38, and an accelerator position sensor 95 that detects an accelerator operation amount ACCP that is an operation amount of an accelerator pedal are connected to the control device 100. Signals from various sensors are input to the control device 100. Further, the control device 100 calculates the engine speed NE based on the output signal of the crank angle sensor 93. The engine load factor KL is calculated based on the engine speed NE and the intake air amount GA.

The control device 100 is configured to recognize the engine operating state based on the detection signals of the various sensors, and to perform various engine controls such as opening degree control of the throttle valve 38, fuel injection control of the fuel injection valve 39, and ignition timing control of the ignition plug 37 according to the recognized engine operating state.

The control device 100 is configured to perform idle rotation speed control for controlling the idle rotation speed of the internal combustion engine to a target idle rotation speed as one of the engine controls. The idle rotation speed control is feedback control including PI control or PID control for adjusting the output torque of the internal combustion engine 1 by a feedback value calculated based on a deviation between the actual idle rotation speed and the target idle rotation speed. The idle rotation speed control is applied on the assumption that the above-described high-viscosity lubricating oil is used, and is performed as follows.

That is, control device 100 calculates the target idle rotation speed, for example, based on the operating state of auxiliary machine 26. Then, the control device 100 calculates the ISC required torque TQI, which is the engine torque at which the target idle rotation speed can be obtained, and performs the opening degree control of the throttle valve 38 and the ignition timing control of the ignition plug 37 so that the calculated ISC required torque TQI can be obtained. In the idle rotation speed control, the opening degree of the throttle valve 38 is controlled so that the intake air amount increases as the required output torque increases, and the ignition timing of the ignition plug 37 is controlled so that the ignition timing is advanced as the required output torque increases.

The ISC required torque TQI is calculated by adding a correction value H to the base torque TQIb (TQI is TQIb + H). The base torque TQIb is, for example, a base value of the ISC required torque TQI calculated based on the target idle rotation speed. The correction value H is a torque value required to compensate for a deviation between the actual engine speed and the target idle speed obtained from the base torque TQIb, and is the sum of the learning value ETQG and the feedback value ETQF (H ═ ETQG + ETQF).

The feedback value ETQF is a value calculated by PI control or PID control, and is a torque value obtained by subtracting an actual idle rotation speed from a target idle rotation speed, that is, a deviation Δ NE between the target idle rotation speed and the actual idle rotation speed. When the actual idle rotation speed is lower than the target idle rotation speed and the deviation Δ NE is a positive value, the feedback value ETQF is a positive value and the absolute value of the deviation Δ NE is set to be larger. Thereby, the actual idle rotation speed is increased toward the target idle rotation speed. In contrast, when the actual idle rotation speed is higher than the target idle rotation speed and the deviation Δ NE is a negative value, the feedback value ETQF is a negative value and the absolute value of the deviation Δ NE is set to be larger. Thereby, the actual idle rotation speed is reduced toward the target idle rotation speed.

The feedback value ETQF is protected by a feedback upper limit protection value FBmx and a feedback lower limit protection value FBmn calculated by a feedback protection value calculation process described later, thereby defining an upper limit and a lower limit of the feedback value ETQF. That is, when the feedback value ETQF calculated based on the deviation Δ NE is a value larger than the feedback upper limit protection value FBmx, the value of the feedback upper limit protection value FBmx is set to the value of the feedback value ETQF. On the other hand, when the feedback value ETQF calculated based on the deviation Δ NE is smaller than the feedback lower limit protection value FBmn, the value of the feedback lower limit protection value FBmn is set to the value of the feedback value ETQF. By the protection processing, when the range between the feedback upper limit protection value FBmx and the feedback lower limit protection value FBmn is set as the feedback range FBR, the output torque is increased or decreased by the feedback control in the feedback range FBR.

The feedback value ETQF is composed of an air quantity feedback value ETQA and an ignition timing feedback value ETQT (ETQF ═ ETQA + ETQT). The air quantity feedback value ETQA is a torque value corresponding to a torque adjustment amount achieved by adjusting the intake air quantity, that is, adjusting the opening degree of the throttle valve 38, among the feedback values ETQF. The ignition timing feedback value ETQT is a torque value corresponding to a torque adjustment amount achieved by adjustment of the ignition timing, that is, adjustment of the amount of advance of the ignition timing, among the feedback values ETQF. A value obtained by subtracting air quantity feedback value ETQA from feedback value ETQF is set as ignition timing feedback value ETQT. Further, such setting of the air quantity feedback value ETQA and the ignition timing feedback value ETQT can be appropriately performed. For example, air quantity feedback value ETQA and ignition timing feedback value ETQT can be calculated based on the following expressions (1) and (2).

ETQA being feedback value ETQF × distribution coefficient K … (1)

ETQT ═ feedback value ETQF × (1-partition coefficient K) … (2)

The distribution coefficient K is a value set in a range greater than "0" and equal to or less than "1", and is a value variably set based on the engine operating state.

The learned value ETQG is a value for compensating for a steady deviation between the actual engine speed and the target idle speed obtained from the base torque TQIb, and is updated based on the feedback value ETQF, for example. For example, if the feedback value ETQF is a positive value and the absolute value is larger than a predetermined value (ETQF > predetermined value) continues, the learning value ETQG is updated by adding a constant value a, which is a positive value, to the learning value ETQG. When the learned value ETQG is updated, the constant value a added at the time of the update is subtracted from the feedback value ETQF, whereby the correction value H is maintained at the same value before and after the update of the learned value ETQG. On the other hand, if the feedback value ETQF is a negative value and the state where the absolute value is larger than the predetermined value (ETQF < the predetermined value) continues, the learned value ETQG is updated by adding a constant value B, which is a negative value, to the learned value ETQG. Further, when the learned value ETQG is updated in this way, the constant value B added at the time of the update is subtracted from the feedback value ETQF, whereby the correction value H is maintained at the same value even before and after the update of the learned value ETQG in this case. The updated learning value ETQG is also held in the memory 120 after the engine is stopped.

The learned value ETQG is subjected to protection processing by an upper limit learned value Gmx and a lower limit learned value Gmn. The upper limit learning value Gmx and the lower limit learning value Gmn are fixed values set in advance based on the results of the application test, for example, the upper limit learning value Gmx is set to a positive value, and the lower limit learning value Gmn is set to a negative value. When the learning value ETQG becomes a value larger than the upper limit learning value Gmx, the value of the upper limit learning value Gmx is set as the value of the learning value ETQG by the guard processing. On the other hand, when the learning value ETQG becomes a value smaller than the lower limit learning value Gmn, the value of the lower limit learning value Gmn is set as the value of the learning value ETQG by the guard processing.

Next, the process of calculating the feedback upper limit guard value FBmx and the feedback lower limit guard value FBmn will be described with reference to fig. 2 to 4.

Fig. 2 shows the processing procedure of the feedback protection value calculation process for calculating the feedback upper limit protection value FBmx and the feedback lower limit protection value FBmn. The processing shown in fig. 2 is realized by the CPU110 executing a program stored in the memory 120 of the control device 100, and the control device 100 repeatedly executes the processing from the start of engine start to the stop of the engine. In the following, the step numbers of the steps shown in the respective processes are indicated by numerals with "S" in the top.

When this processing is started, the control device 100 acquires the current cooling water temperature THW as an index value relating to the engine temperature and acquires the above-described learned value ETQG (S100).

Next, the control device 100 calculates the 1 st upper limit guard value A1mx and the 1 st lower limit guard value A1mn from the following expressions (3) and (4) based on the above-described upper limit learning value Gmx and lower limit learning value Gmn and the learning value ETQG obtained in S100 (S110).

A1mx＝Gmx-ETQG…(3)

A1mn＝Gmn-ETQG…(4)

The 1 st upper limit guard value A1mx is one of guard values that define the upper limit of the feedback value ETQF, and as is clear from fig. 3 and equation (3), the larger the learned value ETQG, the smaller the value of the 1 st upper limit guard value A1 mx. As is clear from fig. 3 and equation (3), since the value obtained by adding the 1 st upper limit guard value A1mx to the learned value ETQG is equal to the upper limit learned value Gmx, the upper limit learned value Gmx also becomes the upper limit guard value of the correction value H equal to the value obtained by adding the feedback value ETQF to the learned value ETQG. Therefore, for example, when the learning value ETQG reaches the upper limit learning value Gmx, the value of the upper limit learning value Gmx is set as the value of the correction value H.

The 1 st lower limit guard value A1mn is one of guard values defining the lower limit of the feedback value ETQF, and as is clear from fig. 3 and equation (4), the value of the 1 st lower limit guard value A1mn decreases as the learning value ETQG increases. That is, the larger the learning value ETQG, the larger the absolute value of the 1 st lower limit guard value A1mn on the negative side. As is clear from fig. 3 and equation (4), since the value obtained by adding the 1 st lower limit guard value A1mn to the learned value ETQG is equal to the lower limit learned value Gmn, this lower limit learned value Gmn also becomes the lower limit guard value of the correction value H equal to the value obtained by adding the feedback value ETQF to the learned value ETQG. Therefore, for example, when the learning value ETQG reaches the lower limit learning value Gmn, the value of the lower limit learning value Gmn is set as the value of the correction value H.

Next, the controller 100 calculates A2 nd upper limit guard value A2mx and A2 nd lower limit guard value A2mn based on the cooling water temperature THW acquired in S100 (S120). The process of S120 is a modification process for modifying the feedback range FBR so as to be wider when the engine temperature is low than when the engine temperature is high.

The 2 nd upper limit guard value A2mx is one of guard values that define the upper limit of the feedback value ETQF, is a positive value, and is set based on the cooling water temperature THW. The 2 nd lower limit guard value A2mn is one of variable guard values defining the feedback value ETQF, and is set to a negative value based on the cooling water temperature THW.

Fig. 4 shows how the 2 nd upper limit guard value A2mx and the 2 nd lower limit guard value A2mn are set based on the cooling water temperature THW.

As shown in fig. 4, when the cooling water temperature THW is equal to or less than the predetermined 1 st water temperature THWa, the 2 nd upper limit guard value A2mx is fixed to a preset value T1. Further, for example, it is preferable to set the highest temperature in the water temperature region at the time of cold of the internal combustion engine 1 to the 1 st water temperature THWa. Further, it is preferable that, for example, a value equal to or less than the upper limit learning value Gmx is set as the value T1.

When the cooling water temperature THW is equal to or higher than the predetermined 2 nd water temperature THWb higher than the 1 st water temperature THWa, the 2 nd upper limit guard value A2mx is fixed to a preset value T2 smaller than the value T1. Further, it is preferable that, for example, the cooling water temperature corresponding to the minimum value of the engine temperature at which the difference in viscosity due to the type of the lubricating oil becomes sufficiently small is set as the 2 nd water temperature THWb. In the present embodiment, when the cooling water temperature THW reaches the 2 nd water temperature THWb, the internal combustion engine 1 is in a warm state.

When the cooling water temperature THW is higher than the 1 st water temperature THWa and lower than the 2 nd water temperature THWb, the 2 nd upper limit guard value A2mx is set to a value between the value T1 and the value T2, and the 2 nd upper limit guard value A2mx is set to be larger as the cooling water temperature THW is lower.

When the cooling water temperature THW is equal to or lower than the 1 st water temperature THWa, the 2 nd lower limit guard value A2mn is fixed to a preset value T4. It is preferable that, for example, the value equal to or larger than the lower limit learning value Gmn be set to the value T4.

When the cooling water temperature THW is equal to or higher than the 2 nd water temperature THWb, the 2 nd lower limit guard value A2mn is fixed to a preset value T3 larger than the value T4.

When the cooling water temperature THW is higher than the 1 st water temperature THWa and lower than the 2 nd water temperature THWb, the 2 nd lower limit guard value A2mn is set to a value between the value T4 and the value T3, and the lower the cooling water temperature THW, the smaller the 2 nd lower limit guard value A2 mn.

Next, the control device 100 calculates the feedback upper limit protection value FBmx and the feedback lower limit protection value FBmn (S130). In step S130, the control device 100 sets the smaller one (smaller in absolute value) of the 1 st upper limit protection value A1mx calculated in step S110 and the 2 nd upper limit protection value A2mx calculated in step S120 as the feedback upper limit protection value FBmx. In step S130, the control device 100 sets, as the feedback lower limit guard value FBmn, the larger one (smaller absolute value) of the 1 st lower limit guard value A1mn calculated in step S110 and the 2 nd lower limit guard value A2mn calculated in step S120. Then, control device 100 once ends this process.

In the present embodiment, the feedback upper limit guard value FBmx is set to a guard value that defines an upper limit of the air quantity feedback value ETQA. Then, a value obtained by subtracting the air quantity feedback value ETQA from the feedback upper limit guard value FBmx is set as a guard value that defines an upper limit of the ignition timing feedback value ETQT. Similarly, the feedback lower limit guard value FBmn is set to a guard value that defines the lower limit of the air quantity feedback value ETQA. Then, a value obtained by subtracting the air quantity feedback value ETQA from the feedback lower limit guard value FBmn is set as a guard value that defines the lower limit of the ignition timing feedback value ETQT.

In addition, for example, a guard value G1 defining an upper limit of air quantity feedback value ETQA and a guard value G2 defining an upper limit of ignition timing feedback value ETQT may be calculated based on the following expressions (5) and (6). For example, a lower limit guard value G3 for the predetermined air quantity feedback value ETQA and a lower limit guard value G4 for the predetermined ignition timing feedback value ETQT may be calculated based on the following expressions (7) and (8).

G1 distribution coefficient KG × feedback upper limit protection value FBmx … (5)

G2 ═ (1-distribution coefficient KG) × feedback upper limit guard value FBmx … (6)

G3 distribution coefficient KG × feedback lower limit protection value FBmn … (5)

G4 ═ (1-distribution coefficient KG) × feedback lower limit guard value FBmn … (6)

The distribution coefficient KG is a value set in a range greater than "0" and equal to or less than "1", and is a value variably set based on the engine operating state.

The operation and effect of the present embodiment will be described below.

(1) As shown in fig. 4, the 2 nd upper limit guard value A2mx, which is a guard value that defines the upper limit of the feedback value ETQF in the idle rotation speed control, is set based on the cooling water temperature THW. More specifically, when the cooling water temperature THW is low, the 2 nd upper limit guard value A2mx is set to a larger value than when the cooling water temperature THW is high. Further, A2 nd lower limit guard value A2mn, which is a guard value defining the lower limit of the feedback value ETQF, is also set based on the cooling water temperature THW. More specifically, when the cooling water temperature THW is low, the 2 nd lower limit guard value A2mn is set to a smaller value than when the cooling water temperature THW is high. The 2 nd upper limit guard value A2mx and the 2 nd lower limit guard value A2mn are set in accordance with the cooling water temperature THW in this manner.

Therefore, in the case where the 2 nd upper limit guard value A2mx is set as the feedback upper limit guard value FBmx and the 2 nd lower limit guard value A2mn is set as the feedback lower limit guard value FBmn, the above-described feedback range FBR shown in fig. 3 becomes wider when the cooling water temperature THW is low than when the cooling water temperature THW is high. Therefore, at a low temperature of the internal combustion engine 1 where a viscosity difference due to a difference in the lubricating oil is likely to occur, the feedback range FBR is wider than that at a high temperature.

If the feedback range FBR is widened in this manner, the adjustment range of the output torque based on the feedback value ETQF is widened. Therefore, even if the engine speed fluctuates greatly as described above at a low temperature of the internal combustion engine 1 due to the use of the low-viscosity lubricating oil, the fluctuation is converged by the adjustment of the output torque. Therefore, the controllability of the engine speed by the idle speed control is improved.

(2) When the cooling water temperature THW is low, the 2 nd upper limit guard value A2mx is set to a larger value than when the cooling water temperature THW is high. Therefore, when the cooling water temperature THW is low, the adjustment range in the direction in which the output torque increases based on the feedback value ETQF becomes wider than when the cooling water temperature THW is high. Therefore, even when the actual idle rotation speed is significantly reduced from the target idle rotation speed at the time of low temperature of the internal combustion engine 1, the output torque can be sufficiently increased, so that the actual idle rotation speed can be increased to converge on the target idle rotation speed.

(3) When the cooling water temperature THW is low, the 2 nd lower limit guard value A2mn is set to a smaller value than when the cooling water temperature THW is high. Therefore, when the cooling water temperature THW is low, the adjustment width in the direction in which the output torque decreases based on the feedback value ETQF increases as compared to when the cooling water temperature THW is high. Therefore, even when the actual idle rotation speed greatly exceeds the target idle rotation speed at the time of low temperature of the internal combustion engine 1, the output torque can be sufficiently reduced, so that the actual idle rotation speed can be reduced to converge to the target idle rotation speed.

(4) At a low temperature of the internal combustion engine, the fuel injected from the fuel injection valve 39 is likely to adhere to the wall surface in the cylinder, so the amount of fuel for combustion in the fuel injected from the fuel injection valve 39 decreases. Therefore, if the fuel injection amount is applied in consideration of the fuel adhesion amount to the wall surface at the time of low temperature, the idle rotation speed becomes stable. Further, since the combustion of the air-fuel mixture is slow at the time of low temperature of the internal combustion engine, if the ignition timing of the ignition plug 37 at the time of low temperature of the internal combustion engine is applied so as to be on the advance side of the ignition timing at the time of high temperature of the internal combustion engine 1 and the combustion pressure in the combustion chamber is appropriately increased, the idle rotation speed becomes stable. However, even if the internal combustion engine is started from a low temperature state, the temperature of the internal combustion engine gradually rises with the passage of time, so it is difficult to maintain the internal combustion engine in a low temperature state during operation. Therefore, it is practically difficult to apply the fuel injection amount and the ignition timing in accordance with the low temperature phase.

In this regard, in the present embodiment, when the coolant temperature THW is low, the feedback range FBR is widened compared to when the coolant temperature THW is high, thereby improving the controllability of the engine speed by the idle speed control. Therefore, even when it is difficult to apply the fuel injection amount and the ignition timing as described above carefully in accordance with the low temperature, the idle rotation speed can be stabilized.

The present embodiment can be modified and implemented as follows. This embodiment and the following modifications can be combined and implemented within a range not technically contradictory to the technology.

The 2 nd upper limit guard value A2mx and the 2 nd lower limit guard value A2mn are both set based on the cooling water temperature THW, whereby the feedback range FBR is widened when the cooling water temperature THW is low as compared with when the cooling water temperature THW is high.

In addition, the feedback range FBR may be widened when the cooling water temperature THW is low as compared with when the cooling water temperature THW is high by setting the 2 nd lower limit guard value A2mn to a fixed value and setting the 2 nd upper limit guard value A2mx based on the cooling water temperature THW. The 2 nd upper limit guard value A2mx may be set to a fixed value, and the 2 nd lower limit guard value A2mn may be set based on the cooling water temperature THW, so that the feedback range FBR is widened when the cooling water temperature THW is low as compared with when the cooling water temperature THW is high.

The 2 nd upper limit guard value A2mx and the 2 nd lower limit guard value A2mn shown in fig. 4 are examples, and the 2 nd upper limit guard value A2mx and the 2 nd lower limit guard value A2mn may be set in another manner.

For example, as shown in fig. 5, when the cooling water temperature THW is equal to or higher than the 2 nd water temperature THWb, the 2 nd upper limit guard value A2mx is fixed to the value T2 and the 2 nd lower limit guard value A2mn is fixed to the value T3. When the cooling water temperature THW is lower than the 2 nd water temperature THWb, the 2 nd upper limit guard value A2mx may be set to a value between the value T1 and the value T2 such that the 2 nd upper limit guard value A2mx is larger as the cooling water temperature THW is lower, and the 2 nd lower limit guard value A2mn may be set to a value between the value T3 and the value T4 such that the 2 nd lower limit guard value A2mn is smaller as the cooling water temperature THW is lower.

As shown in fig. 6, when the cooling water temperature THW is equal to or lower than the 1 st water temperature THWa, the 2 nd upper limit guard value A2mx is fixed to the value T1 and the 2 nd lower limit guard value A2mn is fixed to the value T4. When the cooling water temperature THW is higher than the 1 st water temperature THWa, the 2 nd upper limit guard value A2mx may be set to a value between the value T1 and the value T2 such that the 2 nd upper limit guard value A2mx is larger as the cooling water temperature THW is lower, and the 2 nd lower limit guard value A2mn may be set to a value between the value T3 and the value T4 such that the 2 nd lower limit guard value A2mn is smaller as the cooling water temperature THW is lower.

As shown in fig. 7, when the cooling water temperature THW is equal to or lower than the 1 st water temperature THWa, the 2 nd upper limit guard value A2mx is fixed to the value T1 and the 2 nd lower limit guard value A2mn is fixed to the value T4. When the cooling water temperature THW is higher than the 1 st water temperature THWa, the 2 nd upper limit guard value A2mx may be fixed to the value T2 and the 2 nd lower limit guard value A2mn may be fixed to the value T3.

As shown in fig. 8, when the cooling water temperature THW is equal to or higher than the 2 nd water temperature THWb, the 2 nd upper limit guard value A2mx is fixed to the value T2 and the 2 nd lower limit guard value A2mn is fixed to the value T3. When the cooling water temperature THW is lower than the 2 nd water temperature THWb, the 2 nd upper limit guard value A2mx may be fixed to the value T1 and the 2 nd lower limit guard value A2mn may be fixed to the value T4.

As shown in fig. 9, instead of providing a water temperature range in which the 2 nd upper limit guard value A2mx and the 2 nd lower limit guard value A2mn are fixed values, the 2 nd upper limit guard value A2mx may be set to a value in which the 2 nd upper limit guard value A2mx is larger as the cooling water temperature THW is lower and the 2 nd lower limit guard value A2mn may be set to a value in which the 2 nd lower limit guard value A2mn is smaller as the cooling water temperature THW is lower, over the entire assumed cooling water temperature THW.

Although the cooling water temperature THW is used as the index value of the engine temperature, other values may be used as the index value of the engine temperature. For example, parameters related to the engine temperature, such as the temperature of the lubricating oil of the internal combustion engine 1 and the elapsed time after the engine start, may be used as the index value of the engine temperature.

The control device 100 is not limited to a device that includes a CPU and a memory and executes software processing. For example, a dedicated hardware circuit (e.g., ASIC) may be provided for processing at least a part of the software processing executed in each of the above embodiments. That is, the control device 100 may be configured as any one of the following (a) to (c). (a) The processing device includes a processing device for executing all the above-described processing in accordance with a program, and a program storage device such as a memory for storing the program. (b) The apparatus includes a processing device and a program storage device for executing a part of the above-described processing in accordance with a program, and a dedicated hardware circuit for executing the remaining processing. (c) The apparatus includes a dedicated hardware circuit for executing all of the above-described processing. Here, a plurality of software processing circuits and dedicated hardware circuits may be provided, each of which includes a processing device and a program storage device. That is, the above processing may be executed by a processing circuit including at least one of 1 or a plurality of software processing circuits and 1 or a plurality of dedicated hardware circuits.

Claims

1. A control device for an internal combustion engine performs idle rotation speed control for controlling the idle rotation speed of the internal combustion engine to a target idle rotation speed,

the idle rotation speed control is feedback control for adjusting an output torque of the internal combustion engine by a feedback value calculated based on a deviation of a target idle rotation speed from an actual idle rotation speed,

the control device for an internal combustion engine is configured to execute a protection process and a modification process,

the guard processing is processing of limiting the feedback value by an upper limit guard value and a lower limit guard value,

the modification processing is processing for modifying at least one of the upper limit guard value and the lower limit guard value so that the feedback range is wider when the engine temperature is low than when the engine temperature is high, when the range between the upper limit guard value and the lower limit guard value is set as the feedback range.

2. The control apparatus of an internal combustion engine according to claim 1,

the changing process is a process of changing the upper limit guard value so that the upper limit guard value becomes larger when the engine temperature is low than when the engine temperature is high.

3. The control apparatus of an internal combustion engine according to claim 1 or 2,

the changing process is a process of changing the lower limit guard value so that the lower limit guard value becomes smaller when the engine temperature is low than when the engine temperature is high.